The present invention relates to a cement admixture composition. More particularly, it relates to an admixture composition for hydraulic cement compositions such as mortar and concrete to dramatically improve their workability by preventing decrease in their flowability over sustained periods of time (herein called as "slump loss").
Slump loss is a major problem in the concrete industry. It is highly desired to have a cement additive which will impart high degree of flowability over an extended period of time while not imparting any significant set retardation to the cement composition. Various proposals have been made to solve this problem but, such proposals have not provided a combination of the desired characteristics or only provide the desired characteristics in low degrees.
It is generally known, for example, that the copolymers of alkenyl ethers and maleic anhydride and the derivatives thereof can be employed as cement additives to improve slump loss [Japanese Patent Publication (Kokai) Nos. 285140/1988 and 163108/1990]. However, copolymers of this class which have been previously used, exhibit only small improvement in slump loss or caused excessive set retardation to the treated cement composition.
It has now been found that certain copolymer compositions described below having a specified molecular structure have remarkable effectiveness for the prevention of slump loss without causing significant set retardation.